Water activities in binary and ternary aqueous systems of poly(ethylene glycol), poly(propylene glycol) and dextran

The vapor pressure osmometry (VPO) measurements were used to obtain activities of water for aqueous solutions of poly(ethylene glycol)/dextran and poly(ethylene glycol)/poly(propylene glycol) at temperatures 35°C, 45°C, 55°C and 65°C. The weight fractions of water were varied from 70% to 98%. To increase the accuracy, the calibration constants of the VPO apparatus for each measurement were also determined. The experimental results were used in Flory–Huggins theory to calculate the interaction parameters for the mixtures and the results were discussed in terms of Flory–Huggins theory for evaluating other thermodynamic properties.